Distillation of fatty acids



Jly 2, 1935. l.. M. 'roLMAN DISTILLATION OF FATTY ACIDS Filed April 1, 1955 -,Lll

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Patented July 2, 1935 UNITED STATES DISTILLATION F FATTY ACIDS Lucius M. Tolman, Chicago, Ill., assigner to New Process Fat Refining Corporation, a corporation of Delaware Application April 1, 1933, Serial No. 663,997

3 Claims. (Cl. mi2- 39) This invention relates to improvements in the distillation of fatty acids, and particularly to improvements in the distillation of fatty acids in bubble towers. y 5 In the distillation of fatty acids from a split commercial fat, for example, as described in the co-pending application of Gorano 646,928, and in my co-pending application 645,289, it is advantageous to use a high vacuum in order to permit the use of a lower temperature. It has been found that when proceeding in a bubble tower such as described in the Gorano application referred to, a vacuum in excess of 22 of mercury is difficult to maintain under uniform conditions While maintaining a normal flow of acid and steam. It is of course extremely desirable that whatever vacuum is used should be maintained at a reasonably uniform degree, otherwise any fluctuation may start a chain of results which may increase the fluctuation. For example, a change in the vacuum affects the boiling point of the acids, affects the heat capacity of the steam, and very materially affects the vapor velocity of the gases. 'f

It has now been discovered that the operation of the still may be materially stabilized, andthe Ause of a considerably higher vacuum permitted, by the addition to the bubble tower of a quantity of rings, preferably of the type known as spiral rings and shown in Figs. 2 and 3 of the drawing. A

layer of these rings filling one of the bubble plates has been found to permit stable operation ofthe bubble tower at as much as 2" mercury higher vacuum than without the rings, in spite of the fact that the added resistance of the rings themselves is negligible. About 90 of the space occupied by the rings is free to the passage of vapors.

It has likewise been discovered that the addition of the rings results in an improved color of the distillate. For example, where operation of the bubble tower in normal condition produced a color of 1% N. P. A. from a given stock, the addition of a layer of rings to the top plate in the bubble tower produced a distillate having a color of 1 N. P. A. from the same stock. The action of the rings upon the color of the distillate appears to be most peculiar. For example, if the rings are placed upon a plate containing relatively impure acid-containing stock, the color of the distillate 50 is not improved, but on the contrary appears to be poorer. For example, if rings are placed upon both the top and next to the top plates of the bubble tower, the acid produced had a color of 11A N. P. A. as compared to 1 N. P. A. where merely the top plate contained the rings. The

reason for this appears to be that while prolonging contact of the gases with a substantially pure fatty acid removes entrainment, prolonged contact with even a fairly pure stock such as that contained on the next to the top plate of the tower 5 increases entrainment.

A preferred form ofvring is shown in the draw- I ing. The ring is of quartz, in the form of a pipe section and having within it a thin sheet in the form of a spiral which closes the pipe to move in 10 a direct line through it, the gases being forced to follow the convolutions of the spiral in order to pass through the pipe. As a result gases going through the ring are compelled tochange their direction of movement constantly. 15

By using 1,004 such rings having a diameter of 2%" and being 3" inl height, upon the top tray of a. bubble' tower such as is shown in Fig. 1 of the drawing and is described in Goranflo application Ser. No. 646,928, remarkably improved 20 results are obtained. The tower was 15 feet high, had a cross-sectional area at the top of 30.6 ft. (diameter 6 feet 3"), 'and contained 5 bubble plates 2 feet 6" apart, with the bottom plate 2 feet above the still bottom; the top plate had a 25 liquid capacity of 125 lbs.; liquid acids were passed vinto the tower at the rate of 1420 lbs. per hour 4at a temperature of approximately 500; superheated steam at 700 was introduced at the rate of 940 lbs. per hour; fatty acid -distillate was removed at 30 the rate of 1260 lbs. per hour at a temperature of 440. A Ivacuum of 24" at the tower bottom, 26 at the tower top and 30" on the receiver was used, the atmospheric pressure being 30.5". The bottoms were removed from the still at a. tempera- 85 ture of about 600 and the acids were condensed at a temperature of 300 in the presence of water and under a vacuum of about 28". Under these conditions extremely stable operation was accomplished, there being noappleciable change at any 40` point during a 20-hr. run. At the same time it was possible to maintain the temperature of the tower within a maximum range of 5 at any point. That is, no variationwas shown upon an instrument read to 5. At the same time a color of 1.0 45 N. P. A. was obtained from the same type of stock which under former conditions produced a color of approximately 1% N. P. A. in the same apparatus without the rings.

'Ihe invention is illustrated in the drawing, 50

wherein Fig. 1 represents a 'broken front elevation of a bubble tower and condenser partially cut away to show the layer of rings upon the top tray. The arrangement of rings and bubble caps is purely diagrammatic, it being understood that the layer of rings ordinarily covers the entire plate. Fig. 2 is a plan view of an individual ring, and Fig. 3 is a vertical section along the line 3-3 in Fig. 2, showing the arrangement of the spiral within the ring.

The foregoing detailed description has been given for cleamess of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

I claim:

1. The method of distilling higher fatty acids from fatty acid containing stock which comprises rapidly heating the stock to a volatilizing temperature while passing it in a restricted stream through a heating zone, and passing said stock countercurrent to steam under subatmospheric pressure in a distilling zone whereby fatty acids are vaporized, and removing entrainment from the volatilized fatty acids by passing said gases through and in intimate and direct contact with a body of substantially pure higher fatty acids condensed therefrom substantially free from residuum of the stock, to remove entrainment,

characterized by causing said gases to follow a,

tortuouspath through said fatty acid body substantially free from residuum of the stock whereby the extent of contact with said 'substantially pure fatty acids is substantially increased, and the direction of movement of said gas is frequently changed during such contact. v

2. The method of distilling higher fatty acids from fatty acid containing stock in which the stock is heated to a volatilization temperature while passing in a restricted stream through a heating zone, is discharged under a reduced pressure into a liquid b'ody of fatty acid-containing stock, then successively passed into liquid bodies progressively higher in temperature and lower in fatty acid content, whereby substantially all of vsaid fatty acids are vaporized, and in which steam is passed countercurrent to the flow of the fatty acid stock through said liquid bodies, and the evolved fatty acid vapors mingled with said steam are passed countercurrent to the flow of the fatty acid-containing stock, and in which the gases are passed through and in intimate and drect contact with a liquid body of substantially pure fatty acids condensed at a point in the direction of the movement of the gases beyond the point of inlet of the stock therefrom, characterized by causing said gases to follow a tortuous path through' said substantially pure fatty acid body whereby the extent of contact with said subtantially pure fatty acids is substantially increased, and the direction of movement of said gases is frequently changed during such contact.

3. In the method of distillation of higher fatty acids from fatty acid containing stock, in which open cylinders containing a spiral partition traversing the' length thereof are used to increase the contact of distilled gases with condensed liquid, the step of immersing the cylinders in a body of substantially pure higher fatty acids sub-V stantially free from residuum vof the stock and passing higher fatty acid vapors through said cylinders, whereby the contact of the fatty acid vapors with the pure fatty acid liquid body is materially increased, and the direction of movement thereof is frequently changed during such contact.

' LUCIUS M. TOLMAN. 

